1. Field of the Invention
The present invention relates to an activation method of each part of a communications apparatus with a distortion compensation device (or linearizer).
2. Description of the Related Art
Recently many pieces of radio equipment adopting a linear modulation method with a high frequency utilization efficiency, such as QPSK, etc., have been used. In this case, high linearity is also required by a transmitting unit for transmitting radio waves. If high linearity is required in the power amplifier (PA) installed at the final stage of the transmitting unit, contrarily efficiency degrades, and the requirements on the size, power capacity, radiation, etc., of an amplifier become severe. Specifically, since the use of a power amplifier with a wide power range indicating high linearity inevitably leads to a large PA, power consumption increases and efficiency degrades. Therefore, both high power efficiency and linearity are obtained by using an amplifier with a pretty small power range indicating low linearity in a non-linear range and by linearizing the non-linear area of the small amplifier by a non-linear distortion compensation circuit.
However, there are currently very few commercialization of a transmitting device with sufficient non-linear distortion compensation device (linearizer, in particular a predistortor type linearizer for improving virtual linearity between the input and obtained output of a PA by multiplying the PA input by updateable compensation coefficient and inputting the result to the PA) nor any activation procedure has not been established.
Since a transmitting device with a linearizer must generate many adjustment points and compensation tables compared with a transmitting device without a linearizer, a more complex procedure is required when it is actually activated.
There are conventionally few commercialization of a transmitting device with a sufficient linearizer and it cannot be said that a technology required to control such a device is sufficiently developed. In particular, although in a wideband-CDMA (W-CDMA), the commercialization of which is widely researched and developed, it is considered that a wideband signal is transmitted with high power, it is simultaneously desired that such a device is configured using the small PA described above in order to avoid the large size and high power consumption of the device. Therefore, it can be expected that a transmitting device with a linearizer will be a main stream device in the future. Therefore, in such a transmitting device with a linearizer, a technology, such as a control method of each part, etc., must be sufficiently developed. Since in a transmitting device with a linearizer, many adjustment points and compensation tables must be generated compared with an ordinary transmitting device, the device must be activated by an accurate procedure.